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magazine home > archives > summer 2005 > features

How can the lives of hearing-aid wearers be improved? What are the meanings behind the sounds that infants produce vocally? Professors at the U of M's School of Audiology and Speech-Language Pathology are finding new ways to answer these questions through several ambitious studies.

Sound check
by Jamie Peters

People's voices began fading into an indecipherable blur of sound for Anne Reed in the 1980s, but the ring of the her alarm clock still remained sharp and distinct every morning.

When Evelyn Mills attended her teacher organization's meetings in the mid-1990s, she often would have to pull a friend over to the corner of the room afterward. Words that had once sounded loud and clear now came across muffled, and Mills needed her friend to repeat what others had said during the sessions.

Reed and Mills can recall the first moments of when their hearing began to fade with vivid precision. The two women have a condition that is one of the most common ailments among older adults: hearing loss. According to the National Institute on Deafness and Other Communication Disorders, one in three people older than 60 and half of those older than 85 have experienced hearing loss.

Mills (BS '45), a retired high school teacher since 1988, initially hesitated to seek treatment despite the urging of her friends.

  Robyn Cox

Dr. Robyn Cox has developed scientific questionnaires and continues to test methods for improving fittings for hearing-aid users.

"I was afraid to just pick somebody out of the Yellow Pages because I had heard so many horror stories about people getting treatments that didn't do anything," she says.

In addition, Mills' hearing deterioration was a blow to her self-image. "I didn't want to do it," says Mills, 82. "You know how people are: You don't want to admit that you've got to have hearing aids. This is part of it — it may be vanity."

Reed, who recently turned 80, also postponed getting hearing aids until 1995, although she began to experience gradual hearing loss in 1980. "You get to the point were you don't understand what people are saying, and that's very frustrating," says Reed. "And where you are talking to someone you only hear parts of what people are saying. And I didn't like to be like that."

The same goes for Mills, who ultimately decided to take action by getting fitted for hearing aids at the University of Memphis' School of Audiology and Speech-Language Pathology (AUSP) in 2002.

Both women are also participants in studies conducted by Dr. Robyn Cox, a professor at AUSP, that aim to improve hearing aid fittings among users. Participants donate their time for a primary reason: to benefit younger generations.

"I feel like everybody should do what they can to help future generations coming along," says Reed. "Maybe by testing my hearing they can do more with hearing aids for the people coming after me."

As Cox investigates issues orbiting the short-circuiting of the mysterious wiring inside the human ear, AUSP also bustles with a number of research efforts that explore the equally enigmatic development of human speech. One such study, Dr. Kimbrough Oller's work in infant vocal development, further underscores the innovative and wide-ranging work professors are conducting at the U of M school, which is headed by Dr. Maurice Mendel, dean.

All ears

Evelyn Mills isn't alone in her initial hesitancy to get fitted for hearing aids. Technology has evolved to the point where

in-ear hearing aids are basically invisible; yet the perception that hearing loss means people are past their prime and have difficulty functioning in social situations still persists, says Cox.

"It's just a disorder that has a huge stigma associated with it, and that's a cultural thing," says Cox.

In addition, high costs, which can run between $5,000 and $6,000 for a pair of hearing aids that often only last five years, can be prohibitive to many prospective clients, Cox emphasizes. Furthermore, many people who have made the pricey investments aren't satisfied with the product. "Even a really excellent hearing aid can't give people back the good hearing that they had when they were in their 20s and 30s," Cox says.

But Cox believes more steps can be taken to improve the fitting process.

Cox's research revolves around two primary areas, the first of which she has been pursuing for more than 20 years. This specific focus involves developing scientific methods for measuring to what extent hearing aids help people in their everyday lives. Cox has developed a number of scientific questionnaires designed to get to the root of people's hearing problems from different points of view, including the Abbreviated Profile of Hearing Aid Benefit. This 24-item questionnaire is considered by audiologists to be one of the most widely used self-assessment tools to gauge hearing.

Cox's other research comprises studies that attempt to bore down to a patient's individual issues and qualities in order to more successfully fit him or her with hearing aids. The audiogram is the general instrument clinicians use to judge a person's auditory capability through the use of headphones and a series of tones. But it's also an imperfect means to identify a person's needs, says Cox.

"People that have the same audiogram may have different problems, different lifestyles, and we know that they will have different needs in their daily lives," says Cox. "They have different problems that they want to address. If we ask them what are the three things you want most out of hearing aids, they'll give you different answers."

As a result, Cox is focusing on pinpointing a person's specific problems above and beyond what the audiogram can measure in studies that Reed and Mills have participated in.

"I am coming from a place where if we can be more specific on the ways we put hearing aids on people, we can improve their level of satisfaction," says Cox. "We're still not going to give them normal hearing ever. I'm sorry. I wish we could. But that is not going to happen because nobody can fix the sensory receptors that are broken in there."

Along these lines, Cox is conducting a study funded by the Eriksholm Research Center in Denmark that looks at how peoples' abilities to process sound evolves in different ways over their lifetimes.

The central query of the Eriksholm study, which is funded by hearing aid manufacturer Oticon, is whether measuring the speed a person processes changing stimuli will allow audiologists to program hearing aids more precisely, resulting in a better fit.

"That's kind of the question," Cox says. "Can we specialize our fittings more appropriately by doing the measurements on people's overall perceptual abilities before we ever fit them with the hearing aids?"

The research aims to access some of the untapped powers of hearing aid technology. "We can do more with hearing aids than we know how to do," says Cox. "There's a lot of technical capabilities out there — a huge amount."

Baby talk

Trying to interpret all those squealing and growling sounds that a 6-month-old baby emits as actual speech is like translating a rooster's crow into "Have a nice day."

Kim Oller with student
Dr. Kimbrough Oller and a team of researchers are observing and studying the cryptic vocal sounds that infants emit, which are critical to establishing a foundation for talking.
Kim Oller with Student  

That was the flaw in the thinking among researchers who attempted to "shoehorn" the sounds of infants into speech-like categories before key advances were made in the mid-1970s, says Dr. Kimbrough Oller, who holds AUSP's Chair of Excellence.

"It wasn't speech at all, and to characterize it as speech sounds at all was to misportray it," says Oller.

In a lab located on the fourth floor of the Regional Medical Center in downtown Memphis, a research team led by Oller meticulously analyzes every vocal sound emitted by babies ages 3 to 6 months old in a playroom setting. Four cameras in the room record the baby's actions; a wireless microphone concealed inside a special vest records the baby's vocalizations in the Infant Vocalization Laboratory, which opened in 2002.

"These vocalizations are not some kind of triviality," says Oller. "They're very important."

Squealing, growling and all the sounds in between that a baby expresses during the first months of life reveal the establishment of a neurological foundation for vocal production, which is critical to the formation of speech, says Oller.

The study was funded in 2004 as a five-year research project by the National Institutes of Health and is co-directed by associate professor Dr. Eugene Buder, who examines the details of infant sounds and finds quantifiable ways to characterize them.

"What the baby is proving to us in those very first months of life is that they can control their vocal tracts," Oller says. "They can produce sounds up the larynx, make the vocal chords vibrate in various ways, and they can create contrasts of sound. A series of squeals and a series of growls indicates their ability to produce sounds on purpose."

This is significant because the human is the only species of primate that shows this sort of control over the vocal apparatus, and the human infant shows that kind of control in the first five months after birth. "So we're reaching the strong conclusion that the human infant in those first months is developing something that is absolutely critical as a foundation to talking," Oller says.

Among all the primate species, the human infant is the most altricial, which means it is the most helpless at birth because it requires the longest period of care.

"And consequently we think the vocalizations of the human infant are so elaborate precisely because infants are competing among each other for attention," Oller says.

To observe an array of infant sounds, the research team intentionally alters the baby's surroundings, including situations when the infant's mother is in the room but is focusing her attention elsewhere as if she is talking to someone else, and periods when the baby is alone.

"The reason we have these kinds of circumstances is that we want to evaluate the sense in which the baby produces vocalizations freely," says Oller. "One of the most interesting things that we've observed very clearly is that babies can utilize these categories of sound that we talked about before — for example, squealing — for multiple purposes.

Unlike the nonhuman primates that have to produce the aggressive vocalization in the aggressive circumstance and nowhere else, the human infant can squeal as a complaint or squeal as an exultation. And on the same day within a few moments, the human baby can switch from using a vocalization for one emotional purpose to utilizing it for another."

One key conclusion the research team continues to gather an increasing amount of evidence in support of is that the sounds serve as voluntary indicators of a baby's well-being and fitness. Infants who express abnormal vocalizations may have aberrations in patterns of development, according to Oller.

This work is important in establishing the bridge to an infant's later vocal development, says Oller. As a result, the research team plans to observe the participating infants during the first 30 months of their life through a later stage of vocal development, "canonical babbling," in which the infant produces repetitive syllables that start to resemble speech, according to Oller.

"Obviously, in the long run we're interested in how these events connect with later events about vocal development," he says.

The complexity of this area of study necessitates that it will continue long into the future.

"There isn't expectation that this work will be completed in my lifetime," says Oller. "This is a life's work for me, and a continued effort for students and colleagues into the future."

And that's the type of dedication that ensures the research at AUSP loudly rings with relevance to everyday human functions that are as complicated as they are natural.

AUSP is seeking adult volunteers for hearing studies. If you are interested, please call 901/678-5848.

 

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